Stabilizers for photographic silverhalide emulsions



Patented July 6, 1948 STABILIZERS FOR PHOTOGRAPHIC SILVER.-

HALIDE EMULSIONS Newton Heimbach and Robert H. Clark, Binghamton, N. Y., assignors to General Aniline & Film Corporation, New York, N. Y., a corporation of Delaware Aipplication May 18, 1946, Serial No. 670,687

11 Claims.

This invention relates to the stabilization of light-sensitive silver-halide emulsions, and more particularly to the use of 5,7-diketo-3,4,6triaza indolizines as stabilizers.

It is known in the art that light-sensitive emulsions, such as gelatin silver-halide emulsions, have a decided tendency to fog. The fog may be of two types, namely, yellow fog andchemical (gray) fog. The yellow fog, sometimes referred to as color fog or dichroic fog, is essentially a colloidal deposit of silver, the color intensity and general appearance of which are determined by the minute particle size and degree of subdivision. The flog is chiey yellow in `color and is most apparent in the'lighter portions of a negative. The color may vary, however, and the colloidal silver particles may, for example, appear green by reflected lightA and yellow or redl by transmitted light. The so-called chemical fog, or gray fog, on the other hand, is the more common and iis formed in a number of ways. It may be caused by premature exposure, by excessive ripening of the emulsion, or by the storage of the film, particularly at high temperatures or for unusually long periods of time.

The primary object of the presentv invention is to provide stabilizers or fog inhibiting agents which tend to prevent the formation of chemical fog, in light-sensitive silver-halide emulsions.

A further object is to provide stabilizers or anti-fogging agents for light-sensitive silverhalide emulsions, which do not lower the sensitivity of the emulsion, and which increase its stability.

Still further objects and advantages will appear from the following specification.

We have found that the above objects are accomplished by utilizing 5,7diketo-3,4,6-triaza- 2 indolizines characterized by a structure corresponding to the following general formula:

wherein R may be hydrogen or halogen, e. g.,

chlorine or bromine, and R1 may be hydrogen, aliphatic, such as alkyl, e. g., methyl, ethyl, propyl, butyl, amyl, and the like, alkoxy, e. g., methoxy, ethoxy, propoxy, butoxy, etc., carbalkoxy, e. g., carbomethoxy, carbethoxy, carboprop- Oxy, etc., carboxy, or halogen of the same va1ue as R..

It should be noted that the usefulness of the compounds represented by the above general f'formula is not dependent upon the nature of the phenyl ring so long as the phenyl ring, whether it be substituted or disubstituted, is a part of the indolizine nucleus.

The method for the preparation of the 5.7-

diketo3,4,6-triaza-indolrizines is given in Beil- Since it is impossible to determine the exact course of the reaction with 4respect to the two amino groups of the o-phenylenediamine, the specific location of the phenyl substituents in the resulting indolizine cannot be ascertained with reasonable accuracy. Accordingly, therefore, it

was deemed desirable, for the sake of clarity, to resort to the prefix in naming the phenyl substituents in the examples. For the same reason, it was deemed advisable to list the following 40 specific indolizines prepared according to the above procedure with the corresponding o-phenylenediamines from whichthey were obtained.

o-lhenylenediamines Indolizines o-Phenylenedamine 5,1-aiketo-l,5,a'z-teuahydro-a,4,6-triaza-1,stenza-immane Ihe following examples will serve to illustrate certain ways in which the stabilizers of our invention have been prepared and applied, but are not to be construed as limiting the invention.

Eample I Example II (et y \N/ sN/ Eight gra-ms of 3,4-diaminotoluene were dis solved in 200 cc. of 50% ethyl alcohol to which were added 28 grams of potassium bicarbonate dissolved in 150 cc. of water. To this `solution were added 22.5 grams of cyanogen bromide dissolved inl 50 cc. of 95% ethyl alcohol with rapid 45 stirring. The temperature rose slowly to 50-60 C. .after this -addition ywith the formation of a precipitate. The nal product was crystallized from glacial acetic acid as colorless microscopic prisms which did not melt below 320 C.

Example III dium hydroxide solution, digested for 10 minute-s with charcoal, ltered, and repreoipitated ywith dilute hydrochloric acid. Microscopic buff-colored 6 prisms were obtained which did not melt below 320 C.

In the preparation of an emulsion containing the stabilizers used according to our invention, a solution of the stabilizer in a suitable solvent, such as alcohol -or an alcohol-'water mixture, adjusted to a neutral or slightly alkaline pH, i. e., pH 7.5 to 10, is made up and the solution mixed with the emulsion at any point during its preparation, but preferably during ripening or just .prior to coating in concentrations varying from 25 mg. to 250 mg. per lit-er of emulsion. The actual concentration employed will depend upon the' -type of emulsion used and varies somewhat with the compound used.

The method of testing the stabilizers employed in thefollowing examples consists of coating two lm strips, such las cellulose acetate, `with the same emulsion, one with and one without any sta.- bilizer, storing the emulsions in an incubator for six days at 50 C., then exposing, developing, fixing, and washing the same under standard con'- ditions. The fog 4density or blackening produced in the unexposed areas in the two emulsions `is then measured in a transmission den-sitomete'r-of standard type.

The following examples will serve to illustrate certain ways in which the stabilizers of our invention have been applied, but lare not to be construed as limiting the invention.

Iz'zrampley IV i To 1 kilogram of an ordinary gelatin silver'- bromoiodide emulsion,` mgs. `of the"com pound of Example I were added just prior yto coating. This emulsion, coated on a suitable support, was incubated for 3 to 5` days at 50 C. At the same time, a similar coating with the same emulsion but containing no stabilizer wasl also incubated as a reference type. Both emulsions immediately after coating gave a fog density of 0.02 upon photographic development. After the incubation period, .these two coatings were exposed and developed together in a suitable developer. It was noted that the referencetype containing no stabilizer had a fog density of 0.28, whereas the stabilized coating had aiog density of only 0.08. l

Example V Y Example VI Example IV was repeated with the exception that an equivalent quantity of the compound of Example'II was substituted for the compound of Example I. The results obtained were almost identical with those obtained in E Xample'I.

Further experiments have shown thatemulsions containing stabilizersV in accordance'with Your invention have not only improved keeping qualities (i. e., a reduction in the fog produced by incubation or by' long storage) but have greatly diminished and, in some cases, completely eliminated changes of speed to which some emulsions are susceptible. f'

The stabilizers, which we have described rand 7 employed may be used in various kinds of emulsions. In addition to being useful in Orthochromatic andpanchromatic emulsions, they may also be used in non-sensitized emulsions and X- ray emulsions. If used with'sensitizing dyes they may be added tothe emulsion before or after the dyes are added. The dispersing agents for-the silver-halides may be gelatin or other `colloid such as water-soluble cellulose derivatives, e. g., hydroxy ethyl cellulose, methyl cellulose, carboxy- Oxy-cellulose, low acetyl value cellulose acetate, and-the like. "The stabilizers may also be employed'ingelatiln or other colloid, such as polyamides or a-mixture of gelatin with a polyamide as described in United States Patent 2,289,775; polyvinyl alcohol and jelling compound as described in -United States Patent 2,249,537; polyvinyl acetaldehyde acetal resins and partially hydrolyzed-acetate resins described in United States Patents 1,939,422 and 2,036,092; cellulose derivatives e. g., cellulose nitrate, cellulose acetate, the lower fatty acid esters of cellulose including simple and mixed esters, ethers of cellu- 4containing the stabilizer. y

-Infthe accompanying drawing, the various iigures are enlarged section views of photographic materials having antifoggng layers made ac- .cording to ourinvention. y

As shown in Figure 1, the support i, which .may` be. of any suitable-material such as glass, cellulose ester, synthetic resin, or paper, is provided with .an anti-fogging layer 3, containing one of said 5,7-diketo-3fl-triaza-indolizines .referred to above. The ligl'it-.sensitive emulsion llayer 2 is attached to the anti-logging layer 3.

{Figure 2 illustrates a similar material in which the support l is coated with. a light-sensitive emulsion layer 2, and on the latter side there is provided an anti-fogging layer 3, containing onet of said 5,'7-diketo-3,4,6-triaza-indolizines.

Figure 3.illustrates a nlm or plate of which the support l bears-on one side the light-sensitive emulsion layer 2, and on the other sidean antifogginglayer 3 containing. such 5,'7-diketo-3A-` triaza-indolizinev Figure 4`illustrates a film, plate or paper of which the support I is provided with. theV lightsensitive emulsion layer 2 containing as an antifogging layer such 5,7-diketo-3,4,6triazain dolizines.

I, Since the presence of thesenew compounds -tends toprevent chemical fog whether they are incorporated directly into the emulsion, added to a separate surface or substratum layer, it is understood that the term -photographic materia as employed herein and inthe appended claims, is used in a generic sense to include each of these Apossible applications.

Various modifications .of this invention will occur to persons skilled in the art and it is,

therefore, understood that the patent granted shall only be limited by the appended claims.

We claim: A

I `1. A photographic materialcomprising a base S and a light-sensitive vsilver-halide emulsion carried thereby, said photographic material containing, in -fog inhibiting amount, a compound of the formula;-

wherein R is a member selected from the class consisting of hydrogen an-d halogen, and R1 is a member selected from the class consisting of hydrogen, aliphatic, alkoxy, carbalkoxy, carboxy and halogen groups. l

2. A photographic material rcomprising a base and a light-sensitive silver-halide emulsion carr-ied thereby, said photographic material containing, in fog inhibitingamount, a 5,7diketo-3,4,6 triaza-indolizine of the formula:

3. A photographic material comprising a base and a, light-sensitive silver-halide emulsion carried thereby, said photographic material 4containing, in fog inhibiting amount, a 5,'7-dlketo- 3,4,6-triaza-indolizine of the formula:

5. A photographic material comprising a base and a light-sensitive silver-halide emulsion containing, -in fog inhibiting amount, a 5,'7-diketo- 3,4,6-triaza-indolizine having the general formula:

wherein R is a member selected fromthe class consisting of hydrogen and halogen, and R1 is a member selected from the class consisting of hydrogen, aliphatic, alkoxy, carbalkoxy, carbo and halogen groups. Y

9 6. A photographic material comprising a base and a light-sensitive silver-halide emulsion containing, in fog inhibiting amount, a 5,7-idiketo- 3,4,6-triaza-indolizine of the formula:

6 0 ll /C\ HN N O=JJ (I3 10 7. A photographic material comprising a base and a light-sensitive silver-halide emulsion conl5 taining, in fog inhibiting amount, a 5,7-diketo- 3,4,6-triaza-indolizine of the formula:

o (Li 20 HN/ \N- CH n l 8. A photographic material comprising a base and a light-sensitive silver-halide emulsion containing, in fog inhibiting amount, a 5,'7-diketo- 3,4,6-triaza-indo1izine of the formula: .o

o Il /C HN \N- J; C1 as 9. A photographic gelatine silver-halide emulsion containing from about 25 mgs. to about o 250 mgs. per liter of emulsion of a 5,'7-diketo- 3,4,6-triaza-indo1izine of the formula.:

10. A photographic gelatine silver-halide emulsion containing from about 25 mgs. to about 250 ings. per Iliter of emulsion of a 5,7-diketo3,4,6 triaza-indolizine of the formula:

NEWTON HEIMBACH. ROBERT H. CLARK.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES ?ATENTS Name Date Heimbach Dec. 11, 1945 Number 

